The World's Biggest Mollusks!

What are Mollusks

There are about 93,000 known species of mollusks. There are mollusks which live in the sea, freshwater and on the land. Not only do mollusks live in many different places, they also come in many different sizes and shapes, and behave in many different ways. They are divided into ten classes, of which two have died out. 

What Kinds Of Mollusks Are There?

The biggest group of mollusks is the Gastropods, or snails and slugs. Some snails and slugs live on land, some in the sea or in fresh water. This class accounts for 80% of the total mollusk species. Members of the next biggest group are called Cephalopods, and includes squids, octopuses and cuttlefish. The world's biggest mollusk is a cephalopod, the Colossal Squid, which is in fact the largest known inverbrate. It can grow up to about 39-46 feet, or 12-14 metres. This is longer than a school bus! Thirdly, there are the bivalves, including clams, oysters, scallops and mussels.These all make yummy dishes! Some other classes of mollusks include the "tusk shells", which have a long curved shell, Chitons, whose shells form several plates, like a suit of armor. There are also the Monoplacophores, which were only discovered in 1952 and the Caudofauveata and Aplacophores, which bury themselves in the mud at the bottom of lakes and the sea.

What Do We Use Mollusks For?

Apart from eating them, we also get valuable luxury goods from some mollusks, such as pearls, royal purple dye (which is very expensive) and sea silk which is used to produce fine silk cloth. Their shells have been used as a money in some places in the past. On the other hand, some mollusks also a pest for us. Snails and slugs attack vegetables. A bite from the blue-ringed octopus or a cone shell could kill you unless you get to a hospital!

A Mollusk's Foot

There is a muscular foot under the body of a mollusk. Different mollusks use this foot for different things. A snail or slug moves slowly on its foot. It secretes mucus to help it stick to the surface and slide along. A snail is capable of walking across a razor blade without getting cut! In bivalves like clams, the foot is used for burrowing into sediment. The largest clam in the world is the geoduck. In cephalopods, the foot is used for jet propulsion and the tentacles and arms are actually part of their foot. They propel themselves by ejecting water from their body. For example, the squid ejects water from a cavity within its body. The scallop also knows a similar same trick, and can jet itself along by clamping its shell suddenly shut over and over! 

Most mollusks have only one pair of gills, or even only one gill with which it breathes. The gill looks feathery. Many of them have muscular mouths with tongues and teeth. The teeth are used to scrape bacteria and algae off the rocks.